JPH11288012A - Crystal holding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal holding device which can stably use the non-linear optical crystal of CLBO(Cs Li B6 O10 ) and BBO(β-Ba B2 O4 ), which have deliquescence for a long time. SOLUTION: Non-linear optical elements are installed in a holder main body 2 to which a heater 5 is wound and a heater bobbin 3. They are stored in a housing 10. Extension flanges 8a and 8b having window members 13a and 13b are fitted to the housing 10. Space where non-linear optical crystal is installed is air-tightly held and high purity oxygen gas or the mix gas of high purity oxygen gas and rare gas is filled inside. A gas lead-in path and a gas discharge path are provided for the extension flanges 8a and 8b. Oxygen gas or mix gas is supplied to space where non-linear optical crystal is installed from outside. For always leading in gas from outside, the window members 13a and 13b are not installed and both ends of the extension flanges 8a and 8b are opened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal holding device for holding a nonlinear optical crystal that emits ultraviolet light, and more particularly, to a crystal holding device that can use a nonlinear optical crystal for a long life.

[0002]

2. Description of the Related Art In recent years, attempts have been made to generate ultraviolet light by wavelength conversion using a nonlinear optical crystal and to apply the ultraviolet light to industrial use. The nonlinear optical crystal for use in such _{applications, CLBO (C s L i B} 6 O 10),
_{LBO (L i B 3 O 5} ), BBO (β-B a B
₂ O ₄ ) and CBO (C _s B ₃ O ₅ ) are known.
These crystals are deliquescent, and when left in the air, hydrates form on the surface. When light is incident on the nonlinear optical crystal while the hydrate remains on the surface, a rapid heat rise occurs there, and in some cases, damage such as cracks occurs in the nonlinear optical crystal.

Therefore, in order to use the nonlinear optical crystal for a long time, the nonlinear optical crystal is usually installed in a holding device capable of hermetically sealing, and a specific gas containing no water is sealed in the holding device. There is a need. However,
The applications where the above-mentioned nonlinear optical crystal is used industrially,
Since there was almost no crystal holding device holding the nonlinear optical crystal, there was no published one, and no gas to be filled in the crystal holding device in order to extend the life of the nonlinear optical crystal was known. Was.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to stably deliquesce non-linear optical crystals such as CLBO and BBO over a long period of time. It is to provide a crystal holding device that can be used.

[0005]

As described above, the CLB
Nonlinear optical crystals such as O, LBO, BBO, and CBO have deliquescence, and if left undisturbed in the air, hydrates form on the surface and cannot be used. Therefore, the present inventors installed a CLBO crystal in a crystal holding device capable of airtight sealing,
A crystal holding device in which high-purity nitrogen gas was sealed was fabricated and used. This was to keep the CLBO crystal in a low humidity atmosphere. However, the crystal holding device in which the high-purity nitrogen gas is sealed is, for example, Nd: YAG
When applied to a wavelength converter that emits the second harmonic of the light emitted from the laser device and emits the fourth harmonic (266 nm), the entire rear end face of the CLBO crystal becomes rough with the elapse of operation time, and the Nd: YAG fourth harmonic It was found that the output decreased with the elapse of the operation time.

Next, a high-purity argon gas was sealed in the crystal holding device, and a fourth harmonic of Nd: YAG was emitted in the same manner as described above. However, also in this case, the Nd: YAG fourth harmonic output decreased with the elapse of the operation time. Therefore, a high-purity oxygen gas was further sealed in the crystal holding device, and a fourth harmonic of Nd: YAG was emitted in the same manner as described above. When the high-purity oxygen gas was sealed in the crystal holding device as described above, it was possible to use the CLBO crystal for a long time without lowering the output.

Although the cause is not clear, one of the causes is
It is considered that oxygen (O), which is a component of the CLBO crystal, escapes from the nonlinear optical crystal. That is, although a nonlinear optical crystal such as CLBO originally contains oxygen, it is considered that oxygen is easily released from the crystal as the fourth harmonic of Nd: YAG is generated, and oxygen is released from the crystal. When the CLBO crystal was exposed to the atmosphere of a room where the humidity was kept low (35% or less) and the fourth harmonic of Nd: YAG was emitted in the same manner as described above, the high purity oxygen gas was sealed. Similarly to the above, no decrease in output was observed. Similar effects were obtained with a mixed gas of oxygen gas and a rare gas.

In any case, if oxygen is sealed in the crystal holding device, the output deterioration of the CLBO crystal is considered to be small, which is the case with a mixed gas of oxygen and a rare gas. It is considered that the same effect can be obtained even with the above. Also, instead of enclosing oxygen, a gas introduction path and a gas exit path are provided in a crystal holding device having a structure capable of airtight sealing,
The same effect can be obtained by intermittently supplying oxygen or a mixed gas of oxygen and a rare gas from the gas introduction path. Furthermore, even when using a crystal holding device that is partially open, oxygen or the above-mentioned mixed gas is always introduced from the gas introduction path, and the periphery of the crystal in the crystal holding device is filled with oxygen. By doing so, a similar effect can be obtained. When supplying oxygen or the above mixed gas from the gas introduction path, it is desirable to provide the gas introduction path on the side of the CLBO crystal from which ultraviolet rays are emitted. This is CL
This is to effectively protect the entire rear end face of the BO crystal (the side from which ultraviolet rays are emitted) from becoming rough with the elapse of the operation time.

The above is not only for CLBO crystals,
It is considered that the present invention can be applied to a non-linear optical crystal generally represented by the chemical formula “M _x N _y (B ₃ O ₅ ) _Z ”, such as the above-described LBO, BBO, and CBO crystals having deliquescent properties. Here, M and N represent atomic symbols such as Cs and Li, and x,
y and z are integer values. For example, M = Cs, N = Li,
x = y = 1, when z = 2 _{is, Cs Li B 6 O 10 (} CL
BO).

[0010] Based on the above, the present invention solves the above-mentioned problems as follows. (1) Pure oxygen or a mixed gas of oxygen and a rare gas is sealed in a holding device having an airtightly sealable structure in which a nonlinear optical crystal of M _x N _y (B ₃ O ₅ ) _z that emits ultraviolet light is installed. . (2) the _{M x N y (B 3 O} 5) z or holding device nonlinear optical crystal BBO is installed which emits ultraviolet light, provided with a gas inlet passage on the side ultraviolet from said nonlinear optical crystal is released A gas discharge path is provided, and pure oxygen or a mixed gas of oxygen and gas is always supplied from the gas introduction path. (3) In a holding device having a structure capable of hermetically sealing a nonlinear optical crystal of M _x N _y (B ₃ O ₅ ) _z or BBO which emits ultraviolet rays, a gas introduction path is provided on a side where ultraviolet rays are emitted from the nonlinear optical crystal. Is provided and a gas discharge path is provided, and pure oxygen or a mixed gas of oxygen and gas is intermittently supplied from the gas introduction path.

[0011]

FIG. 1 is a view showing a structure of a crystal holding apparatus according to a first embodiment of the present invention, and FIG. 1 is a sectional view of the crystal holding apparatus according to the present embodiment. In FIG. 1, 1 is CL
This is a BO crystal, and the CLBO crystal 1 is installed in a holder main body 2 formed of pure aluminum. The CLBO crystal 1 is inserted into the recess of the holder body 2,
It is pressed by a leaf spring or the like (not shown) and held so as not to move in the holder main body 2. Both end surfaces of the concave portion are open, light is incident on the CLBO crystal 1 from one end surface, and light is emitted from the other end surface. Reference numeral 3 denotes a substantially cylindrical heater bobbin made of pure aluminum. A thermocouple 4 for controlling temperature measurement is mounted on the outer periphery of the heater bobbin 3, and is made of a nichrome wire or the like coated on the insulating bobbin with an insulating material. A heater 5 for heating the CLBO crystal is wound.

The holder body 2 on which the CLBO crystal 1 is installed is inserted into the heater bobbin 3, and the holder body 2
Is fixed to the heater bobbin 3 by an O-ring 6.
Vacuum flanges are formed on both end surfaces of the heater bobbin 3, and the surfaces where the vacuum flanges and the heat insulating spacers 7a and 7b are in contact are kept airtight. Heat insulation spacers 7a, 7b
Is made of machinable ceramics and has a heat insulating effect. Holes 7a1 and 7b1 through which light passes are provided at the centers of the heat insulating spacers 7a and 7b. Also,
Vacuum flanges are formed on both end surfaces of the heat insulating spacers 7a and 7b. As described above, the surfaces of the heater bobbin 3 that are in contact with the vacuum flange are kept airtight, and the surfaces that are in contact with the extension flanges 8a and 8b described later. Is kept airtight. A heat insulating material 9 is wound around the heater 5, and the thickness of the heat insulating material 9 is such that its outer diameter is a heat insulating spacer 7 a,
7b is selected so as to have substantially the same outer diameter as 7b.

The heater bobbin 3, into which the holder body 2 is inserted, the heat insulating material 9, and the heat insulating spacers 7a and 7b are inserted into a cylindrical heat insulating spacer 11 made of a thin fluororesin material, and the entirety thereof is a ceramic which can be machined. It is stored in the housing 10 formed by. Fluororesin is excellent as a heat insulating material, which enables efficient heating of the CLBO crystal 1. The housing 10, the heat insulating spacers 7a and 7b, and the cylindrical heat insulating spacer 11 are integrally fixed by a screw 12b attached to a corner on the upper surface side of the housing.

On both sides of the heat insulating spacers 7a, 7b, cylindrical extension flanges 8a, 8b are connected, and the extension flanges 8a, 8b are fixed by set screws 12a that pass through the heat insulating spacers 7a, 7b and reach the heater bobbin 3. ing. The extension flanges 8a and 8b are formed of a machinable ceramic, and the surfaces in contact with the heat insulating spacers 7a and 7b are kept airtight as described above. At the other end of each of the extension flanges 8a and 8b, a front window 13 made of synthetic quartz glass and having an antireflection film formed on the surface.
a, a rear window 13b is provided. Front window 13a, rear window 13b
Are extended flanges 8a, 8 by window retainers 14a, 14b.
b. As described above, the crystal holding device of this embodiment includes the extension flanges 8a and 8b and the front window 13 as described above.
a, the rear window 13b, the heat insulating spacers 7a and 7b, and the heater bobbin 3 form an airtight space, and high-purity oxygen gas is sealed in this space.

FIG. 2 is a diagram showing an example of a configuration in a case where the crystal holding device of this embodiment is applied to wavelength conversion. In the figure, reference numeral 20 denotes a crystal holding device of the present embodiment, in which a CLBO crystal 1 is installed.
The BO crystal 1 is heated by the above-described heater 5 and temperature-controlled. Reference numeral 21 denotes a condensing lens, which makes a second harmonic of light emitted by an Nd: YAG laser device (not shown) incident on the condensing lens 21 and converts the light emitted from the condensing lens 21 into light.
The light enters the crystal holding device 20 from the front window 13a of the extension flange 8a. The light incident on the crystal holding device 20 is CLB
The light is condensed near the center of the O crystal 1, is wavelength-converted by the CLBO crystal 1, and the fourth harmonic (266 nm) of the light emitted by the Nd: YAG laser device is emitted from the rear window 13b of the extension flange 8b.

FIG. 3 is a diagram showing the output of the crystal holding device 20 when only argon gas is sealed in the crystal holding device 20 and when high purity oxygen gas is sealed. In addition,
The figure shows the case where the filling pressure of argon gas and oxygen gas is 1 atm, the horizontal axis is time (Hours), and the vertical axis is the relative output of the above 266 nm light (when oxygen gas and argon gas are charged). (Relative output with the output when the elapsed time is 0 as 1). As can be seen from the figure, when argon gas was sealed, the output was reduced, but when high-purity oxygen gas was sealed, the output was hardly reduced. Although the above experiment shows the results when argon and high-purity oxygen gas were respectively sealed in the crystal holding device 20, even when a rare gas such as argon and oxygen gas were mixed, high-purity oxygen gas was sealed. The same effect as in the case of the above is obtained. Incidentally, it has been confirmed that the same effect can be obtained even when the mixing ratio of argon gas and oxygen gas is 3: 1, and the same effect can be obtained up to a mixing ratio of rare gas and pure oxygen of about 5: 1. It is inferred.

FIG. 4 is a view showing a structure of a crystal holding apparatus according to a second embodiment of the present invention. In the present embodiment, a gas introduction path 31 and a gas discharge path 32 are provided in the crystal holding apparatus shown in FIG. 1, and high-purity oxygen gas or a mixed gas of a rare gas and oxygen gas is continuously supplied or intermittently supplied from the gas introduction path 31. This shows a case in which supply is performed. Although the details of the crystal holding device are omitted in FIG. 2, the portions not shown have the same configuration as that of FIG. In FIG. 4, reference numeral 30 denotes a crystal holding device according to the present embodiment.
The LBO crystal 1 is provided, and the CLBO crystal 1 is heated by the above-described heater 5 and temperature-controlled.

A gas introduction path 31 is provided in the extension flange 8b on the rear side (light emission side) of the crystal holding device 30, and an opening / closing valve V1 is provided in the gas introduction path 31. Further, a gas discharge passage 32 is provided in the extension flange 8 a on the front side (light incident side) of the crystal holding device 30.
Is provided with an open / close valve V2. When the oxygen gas or the mixed gas is continuously supplied, the open / close valves V1 and V2 are always opened, and the oxygen gas or the mixed gas is continuously supplied from the gas supply port A of the gas introduction path 31 into the crystal holding device. Is done. When the oxygen gas or the mixed gas is intermittently supplied, the open / close valves V1 and V2 are repeatedly opened and closed in synchronization with each other at regular time intervals.
The oxygen gas or mixed gas supplied from one gas supply port A is intermittently supplied into the crystal holding device.

When the crystal holding device of this embodiment is applied to wavelength conversion, as described with reference to FIG.
, A second harmonic of light emitted by an Nd: YAG laser device (not shown) is incident on the crystal holding device 30 from the front window 13a of the extension flange 8a via the condenser lens. . The light incident on the crystal holding device 30 is CLBO
The light is condensed in the vicinity of the center of crystal 1, wavelength-converted by CLBO crystal 1, and the fourth harmonic (266 nm) of the light emitted from the Nd: YAG laser device is emitted from rear window 13 b of extension flange 8 b.

FIG. 5 is a view showing the structure of a crystal holding apparatus according to a third embodiment of the present invention. In this embodiment, the front window 13a and the rear window 13b shown in FIGS. 1 and 4 are removed to open the front side (light incident side) and the rear side (light exit side) of the crystal holding device, and to extend the front side extension flange. 8a and 8b show a case where gas introduction paths are provided in the rear extension flange 8b. Although the details of the crystal holding device are omitted in FIG. 2, the portions not shown have the same configuration as that of FIG. In FIG. 5, reference numeral 40 denotes a crystal holding device of the present embodiment, in which the CLBO crystal 1 is installed in the crystal holding device 40.
The O crystal 1 is heated and controlled by the heater 5 described above.

Gas introduction passages 41, 41 'are provided in the extension flanges 8a, 8b on the front side (light incident side) and rear side (light emission side) of the crystal holding device 40, and the gas introduction passages 41, 4 are provided.
Opening / closing valves V1 and V1 'are provided at 1'. Both ends of the extension flanges 8a and 8b are opened, and oxygen or a mixed gas supplied from the gas supply port A is discharged to the outside through openings 42 and 42 'at both ends of the extension flanges 8a and 8b. In the present embodiment, as described above, CL
Gas introduction passages 41, 41 'are provided on the front side and the rear side of the BO crystal, and the on-off valves V1, V1' are always opened to close the CL.
An oxygen gas or a mixed gas is continuously supplied to the front and rear sides of the BO crystal. Thereby, the extension flanges 8a, 8b
Can be filled with the above oxygen gas or mixed gas even if both ends of the CLBO crystal are open.
O-crystals can be protected from moisture and the life can be prolonged. When the crystal holding device of this embodiment is applied to wavelength conversion, light enters the crystal holding device 40 from the opening 42 on the front side of the extension flange 8a as in the second embodiment, and C is applied.
The light whose wavelength has been converted by the LBO crystal 1 is emitted from the opening 42 'behind the extension flange 8b.

The arrangement of the gas introduction path and the gas discharge path can be variously modified as follows. FIG. 6 is a diagram showing an example of the arrangement of gas introduction paths and gas discharge paths when the crystal holding device is hermetically sealed. 4A shows the arrangement of the gas introduction path 31 and the gas discharge path 32 shown in FIG. 4, and FIG. 4B shows the arrangement of the gas introduction path 31 and the gas discharge path 32 on the rear end side (light emission side). The example provided in the extension flange 8b is shown. FIG. 3C shows an example in which the gas introduction paths 31 and 31 'are provided on the front and rear end side extension flanges 8a and 8b, and the gas discharge path 32 is provided on the rear end side extension flange 8b. FIG. 3D shows that gas introduction passages 31 and 31 'are provided on front end and rear end extension flanges 8a and 8b, and gas discharge passages 32 and 32' are provided on front end and rear end extension flanges 8a. , 8b.

FIG. 7 shows an extension flange 8a,
It is a figure which shows the example of arrangement | positioning of a gas introduction path and a gas discharge path when both ends of 8b are open. 5A shows the arrangement of the gas introduction paths 41, 41 'shown in FIG. 5, and the introduced gas is supplied to the openings 42, 4 at both ends of the extension flanges 8a, 8b.
Released from 2 '. FIG. 3 (b) shows that a gas introduction path 41 is provided in the rear (light emission side) extension flange 8b, and the introduced gas is supplied to the openings 42, at both ends of the extension flanges 8a and 8b.
FIG. 4C shows a case where the gas is released from the gas discharge path 42 ′, and FIG.
3 shows the case where it is provided on the extension flange 8b.

As shown in FIGS. 6 and 7, by providing the gas introduction path at least on the extension flange 8b on the rear end side (light emitting side), the rear end face (on the side where ultraviolet rays are emitted) of the nonlinear optical crystal is provided. New gas can be supplied, and the entire rear end face can be effectively protected from becoming rough with the elapse of operation time. In the above example, the extension flange 8
Although the case where both ends of a and 8b are closed and the case where both ends are open are shown, the extension flanges 8a and 8b are shown.
May be closed at one end and open at the other end.

[0025]

As described above, according to the present invention,
Is an M that emits ultraviolet light_xN_y(B_ThreeO _Five)_zNon-linear
Pure oxygen or acid is stored in the holding device where the optical crystal is installed.
A mixture of elemental and rare gases is filled or introduced from outside
The nonlinear optical coupling with deliquescent
The life of the crystal can be extended, and the output light of the crystal holding device
Can be suppressed. In addition, a gas introduction
In this case, at least the non-linear optical crystal
By providing on the side where ultraviolet rays are emitted from the rear end face
Effective protection from UV damage
it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a crystal holding device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a configuration in a case where the crystal holding device of the present embodiment is applied to wavelength conversion.

FIG. 3 is a diagram showing an output in a case where only an argon gas is enclosed in a crystal holding device and an output in a case where a high-purity oxygen gas is enclosed.

FIG. 4 is a diagram showing a schematic configuration of a crystal holding device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a crystal holding device according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a modification of the second embodiment.

FIG. 7 is a diagram showing a modification of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CLBO crystal 2 Holder main body 3 Heater bobbin 4 Thermocouple 5 Heater 6 O-ring 7a, 7b Heat insulating spacer 8a, 8b Extension flange 9 Heat insulating material 10 Housing 11 Heat insulating spacer (cylindrical) 13a Front window 13b Rear window 20, 30, 40 Crystal holding Apparatus 31, 41 Gas introduction path 42 Opening 32, 43 Gas release path V1, V2 Open / close valve

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[Procedure amendment]

[Submission date] April 22, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction contents]

[0010] Based on the above, the present invention solves the above-mentioned problems as follows. (1) Pure oxygen or a mixed gas of oxygen and a rare gas is sealed in a holding device having an airtightly sealable structure in which a nonlinear optical crystal of M _x N _y (B ₃ O ₅ ) _z that emits ultraviolet light is installed. . (2) the _{M x N y (B 3 O} 5) z or holding device nonlinear optical crystal BBO is installed which emits ultraviolet light, provided with a gas inlet passage on the side ultraviolet from said nonlinear optical crystal is released A gas discharge path is provided, and pure oxygen or a mixed gas of oxygen and a rare gas is always supplied from the gas introduction path. _{(3) M x N y (} B 3 O 5) that emits ultraviolet _z or the holding device of the hermetic sealable structure BBO nonlinear optical crystal, the gas introduced into the side UV from above Symbol nonlinear optical crystal is released And a gas release path,
Pure oxygen or a mixed gas of oxygen and a rare gas is intermittently supplied from the gas introduction path.

Claims (3)

[Claims] 1. M _x N _y (B ₃ O ₅ ) emitting ultraviolet light
_{What is} claimed is: 1. A holding device for holding a _z- or BBO nonlinear optical crystal, wherein the holding device has a structure capable of hermetically sealing and contains pure oxygen or a mixed gas of oxygen and a rare gas. 2. M _x N _y (B ₃ O ₅ ) emitting ultraviolet light
_A device for holding a nonlinear optical crystal of _z or BBO, comprising: a gas introduction path and a gas discharge path; at least the gas introduction path is provided on a side where ultraviolet light is emitted from the nonlinear optical crystal; A crystal holding apparatus characterized in that pure oxygen or a mixed gas of oxygen and gas is always supplied from an introduction path. 3. M _x N _y (B ₃ O ₅ ) emitting ultraviolet light
_A device for holding a nonlinear optical crystal of _z or BBO, having a structure capable of airtight sealing, comprising a gas introduction path and a gas emission path, at least the gas introduction path on the side where ultraviolet rays are emitted from the nonlinear optical crystal. A pure oxygen or a mixed gas of oxygen and a gas is intermittently supplied from the gas introduction path.